1. Field of the Invention
The present invention generally relates to computer controlled printers and, more particularly, to printers which are capable of printing with different toners.
2. Description of the Prior Art
While many arrangements for printing of indicia on various sheet materials such as paper have been known for many years, the development and widespread use of the computer (and, possibly, personal computers, in particular) has led to many recent advances in printers which enhance image quality, provide high throughput and/or provide additional or a broadened range of capabilities. Thus, at the present time, computer controlled printers are used not only for generation of documents and correspondence but also for publication and even manufacture of items which involve production of a persistent image.
Many such items (e.g. the forms used for personal checks and other financial and business instruments) are processed by machine after or during use and must be standardized with high accuracy while being printed on a material that may include security features which increase material expense using a material that can be reliably sensed by the machine. Similar concerns may be present to greater or lesser degrees in regard to many other manufactured items that may be produced by printing processes, particularly since the development of techniques for digital representation of images at high resolution with more readily manageable amounts of data.
Computer controlled printers are generally designed for the broadest possible range of applications. Therefore, such printers are generally compatible with many different inks or toners, generally provided in developer units (generally in the form of a cartridge or wheeled cart (depending on the size and capacity of the printer) for loading toner into and unloading toner from a print engine, and many different types of materials on which printing is to be performed. For this reason, it is not practical to provide different toners in developer units which are not physically interchangeable.
However, particular qualities desired in the printed product may require specific toners and/or materials. As a particularly familiar example, while the dimensions of 8½″×11″ and so-called A4 paper are somewhat similar, they differ sufficiently to make differences in formatting of text and/or graphics desirable. Therefore, most word processor applications provide codes associated with a given document indicating the chosen paper size and will communicate with connected printers to ascertain the paper size available and correspondence with document format before printing of the document is permitted.
Unfortunately, some applications of computer controlled printers are far more critical and much less readily monitored In the case of photographic images, color toners and inks must be of an appropriate density and opacity and be distributed in the correct quantity in order to render shades of color accurately or in the desired manner. If the application of toner or ink is not correct in quantity or proportion between all primary colors and black, very objectionable distortion of the color gamut results while consuming expensive, high-quality paper stock often having an expensive finish applied simulating photographic papers. (Such distortions are sufficiently evident and objectionable that many high-quality printers provide for adjustment of printing control parameters based on the number of copies made after each replenishment of toner.) High speed printers can consume large quantities of such expensive printing stock before a color error due to incorrect toner or printer control parameter is discovered.
An even more critical example is the case of check forms, alluded to above, which require a toner, referred to as MICR (Magnetic Ink Character Recognition), having specific magnetic properties in order to be later processed by specialized machinery at the high speed. Such automation of processing is made necessary by high volume of daily current usage of such forms. The stock on which such forms are generally printed normally includes security features to protect against modification attempting to alter the monetary value thereof. Thus, if a MICR or other required toner is not used when required to develop certain required properties of the printed indicia, the printed article may be unusable and worthless while a potentially large quantity of expensive stock has also been consumed. Conversely, if the correct toner is used on improper stock, potentially usable documents which are particularly susceptible to fraudulent modification may be produced.
Unfortunately, neither the nature of the toner nor the nature of the stock on which printing is to be performed is readily detectable by the printer unless very expensive and sophisticated sensors (e.g. density sensors or page readers), intended to respond to relatively subtle differences in materials (and which may also be susceptible to errors and result in effective inoperability of the printer for that reason) are employed. Such a possibility is in marked distinction to the simplicity and reliability of sensing paper size alluded to above.
It should also be appreciated that printers used in such high precision printing operations are often quite expensive and high throughput levels must be maintained. Further, it is common for some indicia to be changed for each document printed such as check or form numbers so that each document can be uniquely identified. Therefore, the information input rate to the printer must be very high and may be derived from several data processors. For this reason, printers in such applications will often be provided with a dedicated processor for management of the routing of print jobs to various printers that may be grouped together (e.g. with different combinations of toner and printing stock provided by each individual printer) or print engines in a unitary printer. Such a dedicated processor is referred to as an advanced function common control unit (AFCCU).
Since a plurality of printers and/or print engines could be controlled by a single AFCCU, for convenience, the particular toner provided by a connected printer or print engine has been set in hardware such as by the setting of a print engine operating point table in non-volatile memory internal to the AFCCU. The print engine operating point table is specific to each toner that can be used in a particular printer and contains data that alters operating parameters as copies are made to provide compensation of operating points of the printer and thus maintain consistent print quality as well as containing coded information identifying the toner loaded in the printer. This storage arrangement is hardware efficient since the same operating point table can supply compensation data for multiple printers but increases the amount of data which must be sent to a given printer unless stored in the printer, as is often preferred.
Therefore, the AFCCU would prevent forwarding of a print job which specified a particular toner where the memory code indicated that the specified toner was not provided. The print engine operating point table in memory is generally set by a customer engineer (CE) at the time a particular connected printer was dedicated to the use of a particular toner such as MICR.
However, if the CE failed to set the memory, the AFCCU would not be able to discern that such a dedicated printer having a specified toner was connected and a print job specifying a toner to which the printer was dedicated would not be forwarded to it. Conversely, since printers and print engines can accept a variety of toners there is no convenient way for a change of toner to be communicated from a printer to its controlling processor or even the AFCCU. Perhaps more importantly, the AFCCU only recognizes and controls printers at the level of its own ports and any disconnection and erroneous reconnection of printers, even when the toners to which the respective printers or print engines are dedicated are supplied, may result in print jobs being sent to printers and printed using materials other than those specified or being blocked from transmission to printers even when the specified materials are, in fact, available therein.
Additionally, to support high throughput levels while minimizing operating costs of a printer, it is desirable that routine maintenance such as replenishment of toner can be performed by the operator of the printer (e.g. the customer of the manufacturer of the printer) and that the need for service by a CE (generally an employee of the manufacturer of the printer) be minimized, although it may be preferred that dedication of a printer or print engine to specialized toners such as MICR or color toner be performed by a CE.
It is similarly desirable that the operator be able to change types of toners which are not of the special purpose type without need for intervention by a CE so that the full versatility of the printer can be used with minimal added expense and down time. Such provisions are known but are not consistent with special type toners that may require distinct printer control parameters and also lead to errors in printing jobs that may specify particular toners, as alluded to above or even preclude any protection against use of the incorrect toner. Unfortunately, the system architecture including an AFCCU and the need for resetting of associated printer control parameters upon change (or replenishment) of special type toner has not permitted such service to be performed by the customer/operator consistent with the possible use of special type toners.
In summary, practical considerations at the present state of the art has made the set up and maintenance of high performance printers very counter-intuitive, inconvenient and susceptible to costly errors and waste of valuable materials, particularly for the user who must endure down-time and service expense of a CE when toner is to be changed in a printer or when printers must be disconnected from and reconnected to an AFCCU or any other difficulty encountered. Further, the conventional arrangements in regard to printers at the present state of the art do not lead to a high confidence level that print jobs are executed properly and with the proper materials even when the system appears fully functional and operational.